1. Field of the Invention
The present invention relates to a ceramic heater and more particularly to a ceramic heater having improved durability.
2. Description of the Prior Art
Conventionally, such electric heating alloys as Ni--Cr--(Fe) and Fe--Cr--Al have been widely used as a heating element for heating or ignition use. Non-metallic elements composed of such materials as silicon carbide, zirconia, molybdenum silicide, lanthanum chromite, and carbon are also commercially available.
As nickel-chromium alloy is easily oxidized, the heating element composed of the alloy is used under limited conditions. Also the element may decrease gradually in cross sectional area by oxidation. This, in turn, will give rise to severe local heating, which may result in self burn-out of the element.
Non-metallic materials described above are not so widely used as is nickel-chromium alloy, because of their low oxidation resistance or high fabrication cost.